Geometrical instrument



Feb.'25, 1958 P. AsPERGER 2,824,377

GEoMETRIcAL INSTRUMENT Filed sept. 22, 1955 l Paul './Idpergr' INVENToR.

` l BY v o; ,gaf @MM/f Arron/uff United States Patent Ofce 2,824,377Patented Feb. 25, 1958 GEOMETRICAL INSTRUMENT Paul Asperger, Flint,Mich. Application September 22, 1955, Serial No. 535,925

8 Claims. (Cl. 33-158) attachment readable with calibrations on theblade or rule and with the other end constructed for marking ormeasuring distances between two points.

Another object of the invention is to provide in a device of thecharatcer set forth, a novel clamping construction for adjustably,rigidly, and accurately attaching trammel heads upon a blade orrule-like beam.

A further object of the invention is to provide, in a device ofthecharacter indicated, a novel construction whereby a single pair ofcaliper legs attached to a pair of trammel heads and aligned withgraduations on a blade or rule-like beam can be used for both inside andoutside measurements.

It is also an object of the invention to provide a device of theabove-indicated character which is simple and' substantial inconstruction, economical to manufacture, and thoroughly eflicient andpractical in use.

These, together with various auxiliary features and objects of theinvention which will later become apparent as the following descriptionproceeds, are attained by the present invention, a preferred embodimentof which has been illustrated, by way of example only, in theaccompanying drawings, wherein:

Figure l is a front elevation of a pair of the improved trammel headsattached to a calibrated blade of a square for use of the device as acompass or dividers;

Figure 2 is a rear elevation of one of the trammel heads showing thesame attached to a portion of a square blade;

Figure 3 is an end view of the same;

Figure 4 is an enlarged vertical section taken on line 4--4 of Figure l;

Figure 5 is also an enlarged sectional view, but is taken on line 5-5 ofFigure 4;

Figure 6 is an enlarged fragmentary front elevation` showing a caliperleg attached to a trammel head which.

has been broken away; and

Figure 7 is a vertical section taken on line 7-7 of Figure 6.

Referring now more specifically to the accompanying drawing wherein likenumerals designate similarA parts throughout the various views, thenumeral 10 indicates generally a detachable blade of a machinistssquare'having on opposite sides and along both longitudinal edgesthereof graduations 11. While the blade of a machinists squareis shownfor the purpose of illustration, it is to be understood that the memberlil may be a steel rue or'any lether type of straightedge havingftat'sides, parallel edges'.

and of a thickness similar to that of a square blade or steel rule.

The improved trammel head forming the subject matter of this inventionhas a main body member 12 which is substantially C-shaped consisting ofa straight and relatively long bight portion 13 and short upper andlower parallel arms 14 and 15, respectively, which are also straight andare joinedl to said bight portion with sharp right-angle corners. Theinner surfaces of the arms 14 and 15 are spaced apart a distancesubstantially equivalent to, but slightly in excess of, the width of theblade 1t? so that said blade may be received between the spaced arms 14and 15 and be embraced by said bight portion 13 and arms 14 and 15.Extending entirely through the lower arm 15 and parallel with the bightportion 13 is a bore 16 into which an indicator leg 17 is received and.held in place by a set screw 1S. The indicator leg 17 has a pointer 19on its lower end and another pointer 20 on its upper end. Also the upperend of the indicator leg 17 is cut away to provide a flat surface 21,which is in surface en.- gagement with a side of the blade 1t) atgraduations 11 along one edge of said blade. lt will be observed inFigure 4 of the drawings that one side of the blade 10 is in surfaceengagement with the bight portion 13 of the body member, the oppositeedges of the blade 10 are in close proximity to the inner side of thearms 14 and 15, and the ilat 21 on the indicator leg is in surfaceengagement with the side of the beam 10 opposite to that engaged andembraced by the bight portion 13.

The upper arm 14 is entirely bifurcated, as at 22, and` receives in saidbifurcation one leg 23 of a substantially L-shaped clamping member 24,said clamping member being pivotally mounted on and carried by the bodymember 12 by a pair of aligned pivot pins 2S threaded in the forkedportions of the arm 14 and having tapered inner ends 26 thereof receivedin like-shaped recesses in opposite sides of the leg 23 of said clampingmember. The other leg 27 of the clamping member extends downwardly inrear of the bight portion 13 of the body member 12 and has a thumb screw28 threaded therethrough that engages the rear side of the bight portion13 for forcing the leg 23 downwardly and into engagement with the.

upper edge of the blade 10 upon inward threading movement of the thumbscrew 28. It will be observed by referring to Figure 4 that theundersurface 29 of the leg 23, when in engagement with an edge of theblade 10, is at a slight acute and undercut angle to the surface alongthe edge of the blade 10 for holding said blade 10 back and against thebight portion 13.

The leg 23 of the clamping member 24 has a threaded opening 30 extendingdownwardly therein into which is threaded the lower end of a post 31onto which is rotatably mounted a linger-gripping knob 32 for convenientmanipulation of the device when used for any of the purposesabove-designated. It will be further observed that when the surface 29of the leg 23 of the clamping mernber 24 is in clamping engagement withan edge of the blade 10, the post 31 and the axes of the finger-engagingknob 32 are in direct alignment with the indicator leg 17.

In Figures 6 and 7, there is shown an indicator leg 17a which has theupper portion thereof constructed identical to that of the indicator leg17, but has substantially the lower half thereof reversely bent, as at17h, with the pointer 19a thereof slightly rounded and in directalignment with an imaginary straight line along the center line of theup.-l per pointer 28 and tangent at the pointer 19a. Indicator legs ofthis character used upon a pair of trammel headsv clamped to a blade orrule-like straightedge provide both inside and outside beam calipers,and the change from one to the other only requires transferring thetrammel heads to opposite ends of the rule-like beam.,

When adjusting the trammel head along the rue-like beam, the thumb screw28 is loosened to relieve locking pressure on the edges of said beam,and because of the construction and arrangement of the upper end of theindicator leg 17 and close association of the bight portion 13 and botharms 14 and 15 with said beam, said body member is` slidably retained onand relative to said beam. When clamping the trammel head in adjustedposition, the angled undercut lower surface 29 of the leg 23 of theclamping member 24 not only clamps on the edges of the beam, but alsoforces and holds the bight portion of the body member in surfacefrictional contact with a side of the rule-like beam.

From the foregoing description, it can be seen that there is provided atrammel head and indicator attachments thereto for use, eithersingularly or in pairs, upon a rule-like beam to provide a beam compass,beam dividers, beam calipers, or as either a height gauge or a surfacegauge.

In view of the above description, taken in conjunction with theaccompanying drawings, it is believed that a clear understanding of theconstruction, operation, and advantages of the improved trammel headwill be quite apparent to those skilled in this art. A more detaileddescription is accordingly deemed unnecessary.

It is to be understood, however, that even though there is herein shownand described a preferred embodiment of the invention, various changesmay be made without departing from the spirit and full intendment of theinvention.

What is claimed is:

l. A trammel head comprising, in combination with a stiff rule-likebeam, a substantially C-shaped body member closely embracing one sideand opposite edges of said rule-like beam wiith its bight portion andthe spaced arms respectively, said arms of said C-shaped body memberhaving their free ends extended beyond the opposite side of saidrule-like beam and one arm being provided with a bore therethrough thatis parallel with the bight portion of said body member and has thecenter thereof spaced from the inner embracing surface of said bightportion substantially the thickness of said rule-like beam, an indicatorleg positioned in said bore and having a ilat on a side and at one endthereof, said at being in surface engagement with the side of saidrule-like beam opposite to that embraced by said bight portion,attaching means for detachably supporting said leg in said bore, and aclamp movably mounted at and relative to the other arm of said C-shapedbody and arranged to apply pressure on the edge of said rule-like beamadjacent thereto and thereby force the opposite edge of said rule-likebeam against and in frictional contact with the first-mentioned arm.

2. A device as dened in claim 1 wherein said rule-like beam hasgraduations along edges thereof and wherein said end of said leg havingsaid at is also tapered to a point and is registrable with graduationson said rule-like beam.

3. A trammel head comprising, in combination with a stil rule-like beamhaving graduations along edges thereof, a substantially C-shaped bodymember closely embracing one side and opposite edges of said rule-likebeam with its bight portion and the spaced arms respectively, said armsof said C-shaped body member having their free ends extended beyond theopposite side of said rulelike beam and one arm being bifurcated whilethe other 1s provided with a bore therethrough that is parallel with thebight portion of said body member, an indicator leg positioned in saidbore and having a iiat on a side and at one end thereof, said fiat beingin surface engagement with the side of said rule-like beam opposite tothat embraced by said bight portion, a set screw for detachablysupporting said leg in said bore, and a clamp member plvotally mountedin the bifurcated arm of said C-shaped body member and arranged forapplying pressureA on the,

4 edge of said rule-like beam adjacent thereto upon movement on itspivot and thereby force the opposite edge of said rule-like beam againstand in frictional Contact with the first-mentioned arm.

4. A trammel head comprising, in combination with a stiff rule-like beamhaving graduations along edges thereof, a substantially C-shaped bodymember closely embracing one side and opposite edges of said rule-likebeam with its bight portion and the spaced arms respectively, said armsof said C-shaped body member having their free ends extended beyond theopposite side of said rule-like beam and one arm being bifurcated whilethe other is provided with a bore therethrough that is parallel with thebight portion of said body member, an indicator leg positioned in saidbore and having a flat on a side and at one end thereof that is insurface engagement with the side of said rule-like beam opposite to thatembraced by said bight portion, a set screw for detachably supportingsaid leg in said bore, a clamping member pivotally mounted in thebifurcated arm and engageable with the edge of the rule-like beamadjacent thereto, and a thumb screw threaded through said clampingmember and engaging said body member for moving said clamping member onits pivot and into engagement with said edge of said rule-like beam.

5. A device as defined in claim 4, wherein a rotatable finger-grippingknob is provided on the pivoted clamping member and is offset therefromin a direction opposite to that in which said leg extends for convenientmanipulation of the device.

6. A trammel head comprising, in combination with a stiff rule-like beamhaving graduations along edges thereof, a shouldered body memberslidable along said rulelike beam and closely embracing one side and oneedge of said rule-like beam, a clamping member movably mounted on saidbody member and arranged for applying frictional pressure on the edge ofsaid rule-like beam opposite to that embraced by said body member forholding said body member against movement relative to said rule-likebeam, an indicator leg detachably carried by said body member at alocation adjacent embracement thereof with an edge of said rule-likebeam, a flat on a side and at an end of said indicator leg, said iiatbeing in surface engagement with the side of said rule-like beamopposite to that embraced by said body member, and a pointer on each endof said indicator leg, said pointer on the end of said leg having saidflat being registrable with the graduations on said rule-like beam.

7. A device as defined in claim 6, wherein the indicator leg isreversely bent at a location outwardly of its attachment to the bodymember and wherein an imaginary straight line along the center line ofthe pointer at the graduations and tangent at the pointer at the end ofsaid reversely bent end portion is at right angles to the edges of therule-like beam.

8. A trammel head comprising, in combination with a stiff rule-like beamhaving graduations along edges thereof, a substantially C-shaped bodymember closely embracing one side and opposite edges of said rule-likebeam with the bight portion and the spaced arms thereof respectively,said arms of said C-shaped body having their free ends extended beyondthe opposite side of said rulelike beam and one arm being bifurcatedwhile the other is provided with a bore therethrough that is parallelwith the bight portion of said body, an indicator leg attached in saidbore and registrable with the graduations on the rule-like beam, saidindicator leg having a tiat on its side at one end thereof that is insurface engagement with the side of said rule-like beam opposite to thatembraced by said bight portion, a substantially L-shaped clamping memberpivotally mounted in the bifurcated arm and having a flat surface on oneleg thereof that is engageable with the edge of the rule-like beamadjacent thereto, and a thumb screw threaded in the other leg of saidclamping member and engaging said body References Cited in the le ofthis patent UNITED STATES PATENTS Johnston Nov. 9, 1937v Vierling Nov.21, 1944 FOREIGN PATENTS France uly 7, 1947

